What Actually Happens in the First Sixty Seconds
The first minute of a session produces charts that look nothing like the rest of the day. Long bars, sharp reversals, volume that dwarfs anything for hours afterwards. The usual explanation is volatility, which is a description rather than a cause. The behaviour has specific mechanical reasons, and knowing them changes how much weight the minute deserves.
The Book Has Just Been Emptied
The opening auction exists to match accumulated orders at a single price. When it resolves, a large part of the resting interest that had built up overnight has been consumed. Continuous trading then begins against whatever is left, which is considerably less than what was there a moment earlier.
A thin book means each order travels further before it finds the other side. The same quantity that would barely register an hour later can move price noticeably, and it does so without anyone having formed a new opinion about anything. Much of the movement in the opening minute is the market rebuilding its depth rather than participants disagreeing about value.
Not Everyone Arrives at the Same Time
The participants active in the first seconds are not a cross section of the day's participants. Automated systems act immediately. Those who submitted orders into the auction have already acted and are now watching. A large group of discretionary participants deliberately waits to see the opening price before doing anything, which means their orders arrive in a wave that follows the initial move rather than joining it.
That sequencing produces a characteristic shape. An initial push, driven by whoever was fastest into a thin book, followed by a second wave of interest reacting to that push, which frequently pushes back against it. What looks like a reversal on conviction is often just the slower half of the market arriving.
Market Makers Are Recalculating
The firms that normally provide continuous two sided quotes have the least information at the open and the most exposure to being wrong. Their response is to widen, quote in smaller size, or step back briefly while they establish where fair value sits after the auction.
This is rational on their part and expensive for everyone else. A wide spread is a direct cost on entry and another on exit, and quoted size that is smaller than usual means an order that would ordinarily fill in one piece now walks through several levels. Both effects fade over the following minutes as confidence returns, which is why the same order costs measurably less a few minutes later.
Overnight Information Is Being Resolved
Anything that happened while the market was closed has had no continuous trading in which to be priced. Whatever the auction produced is a first attempt at that pricing, made with limited participation, and the minutes afterwards are where it gets tested against a wider set of opinions.
On quiet days this resolves quickly and the instrument settles. On days with real overnight news it does not, and the first minute is the beginning of a longer process rather than a self contained event. The two look almost identical while they are happening, which is one reason the minute is so hard to read in real time.
What the Minute Is Worth
The movement is real in the sense that trades happened at those prices. It is unreliable in the sense that the levels reached often reflect a temporary shortage of liquidity rather than agreement between buyers and sellers. A high made in the first minute may never be revisited, and it may also have been set by an order that would not have moved price at all an hour later.
For anything that depends on levels meaning something, that is a serious problem. A range built to include the first minute inherits its extremes from the least reliable stretch of the session. The minute is worth watching closely and worth being cautious about using, and those two positions are entirely compatible.